INSTALL

Building and installing a packaged release of jemalloc can be as simple as
typing the following while in the root directory of the source tree:

    ./configure
    make
    make install

If building from unpackaged developer sources, the simplest command sequence
that might work is:

    ./autogen.sh
    make dist
    make
    make install

Note that documentation is not built by the default target because doing so
would create a dependency on xsltproc in packaged releases, hence the
requirement to either run 'make dist' or avoid installing docs via the various
install_* targets documented below.

=== Advanced configuration =====================================================

The 'configure' script supports numerous options that allow control of which
functionality is enabled, where jemalloc is installed, etc.  Optionally, pass
any of the following arguments (not a definitive list) to 'configure':

--help
    Print a definitive list of options.

--prefix=<install-root-dir>
    Set the base directory in which to install.  For example:

        ./configure --prefix=/usr/local

    will cause files to be installed into /usr/local/include, /usr/local/lib,
    and /usr/local/man.

--with-version=<major>.<minor>.<bugfix>-<nrev>-g<gid>
    Use the specified version string rather than trying to generate one (if in
    a git repository) or use existing the VERSION file (if present).

--with-rpath=<colon-separated-rpath>
    Embed one or more library paths, so that libjemalloc can find the libraries
    it is linked to.  This works only on ELF-based systems.

--with-mangling=<map>
    Mangle public symbols specified in <map> which is a comma-separated list of
    name:mangled pairs.

    For example, to use ld's --wrap option as an alternative method for
    overriding libc's malloc implementation, specify something like:

      --with-mangling=malloc:__wrap_malloc,free:__wrap_free[...]

    Note that mangling happens prior to application of the prefix specified by
    --with-jemalloc-prefix, and mangled symbols are then ignored when applying
    the prefix.

--with-jemalloc-prefix=<prefix>
    Prefix all public APIs with <prefix>.  For example, if <prefix> is
    "prefix_", API changes like the following occur:

      malloc()         --> prefix_malloc()
      malloc_conf      --> prefix_malloc_conf
      /etc/malloc.conf --> /etc/prefix_malloc.conf
      MALLOC_CONF      --> PREFIX_MALLOC_CONF

    This makes it possible to use jemalloc at the same time as the system
    allocator, or even to use multiple copies of jemalloc simultaneously.

    By default, the prefix is "", except on OS X, where it is "je_".  On OS X,
    jemalloc overlays the default malloc zone, but makes no attempt to actually
    replace the "malloc", "calloc", etc. symbols.

--without-export
    Don't export public APIs.  This can be useful when building jemalloc as a
    static library, or to avoid exporting public APIs when using the zone
    allocator on OSX.

--with-private-namespace=<prefix>
    Prefix all library-private APIs with <prefix>je_.  For shared libraries,
    symbol visibility mechanisms prevent these symbols from being exported, but
    for static libraries, naming collisions are a real possibility.  By
    default, <prefix> is empty, which results in a symbol prefix of je_ .

--with-install-suffix=<suffix>
    Append <suffix> to the base name of all installed files, such that multiple
    versions of jemalloc can coexist in the same installation directory.  For
    example, libjemalloc.so.0 becomes libjemalloc<suffix>.so.0.

--with-malloc-conf=<malloc_conf>
    Embed <malloc_conf> as a run-time options string that is processed prior to
    the malloc_conf global variable, the /etc/malloc.conf symlink, and the
    MALLOC_CONF environment variable.  For example, to change the default chunk
    size to 256 KiB:

      --with-malloc-conf=lg_chunk:18

--disable-cc-silence
    Disable code that silences non-useful compiler warnings.  This is mainly
    useful during development when auditing the set of warnings that are being
    silenced.

--enable-debug
    Enable assertions and validation code.  This incurs a substantial
    performance hit, but is very useful during application development.
    Implies --enable-ivsalloc.

--enable-code-coverage
    Enable code coverage support, for use during jemalloc test development.
    Additional testing targets are available if this option is enabled:

      coverage
      coverage_unit
      coverage_integration
      coverage_stress

    These targets do not clear code coverage results from previous runs, and
    there are interactions between the various coverage targets, so it is
    usually advisable to run 'make clean' between repeated code coverage runs.

--disable-stats
    Disable statistics gathering functionality.  See the "opt.stats_print"
    option documentation for usage details.

--enable-ivsalloc
    Enable validation code for malloc_usable_size() and sallocx(), which
    verifies that pointers reside within jemalloc-owned extents before
    dereferencing metadata.  This incurs a minor performance hit, and causes
    the functions to return 0 for failed lookups.

--enable-prof
    Enable heap profiling and leak detection functionality.  See the "opt.prof"
    option documentation for usage details.  When enabled, there are several
    approaches to backtracing, and the configure script chooses the first one
    in the following list that appears to function correctly:

    + libunwind      (requires --enable-prof-libunwind)
    + libgcc         (unless --disable-prof-libgcc)
    + gcc intrinsics (unless --disable-prof-gcc)

--enable-prof-libunwind
    Use the libunwind library (http://www.nongnu.org/libunwind/) for stack
    backtracing.

--disable-prof-libgcc
    Disable the use of libgcc's backtracing functionality.

--disable-prof-gcc
    Disable the use of gcc intrinsics for backtracing.

--with-static-libunwind=<libunwind.a>
    Statically link against the specified libunwind.a rather than dynamically
    linking with -lunwind.

--disable-tcache
    Disable thread-specific caches for small objects.  Objects are cached and
    released in bulk, thus reducing the total number of mutex operations.  See
    the "opt.tcache" option for usage details.

--disable-munmap
    Disable virtual memory deallocation via munmap(2); instead keep track of
    the virtual memory for later use.  munmap() is disabled by default (i.e.
    --disable-munmap is implied) on Linux, which has a quirk in its virtual
    memory allocation algorithm that causes semi-permanent VM map holes under
    normal jemalloc operation.

--disable-fill
    Disable support for junk/zero filling of memory.  See the "opt.junk" and
    "opt.zero" option documentation for usage details.

--disable-zone-allocator
    Disable zone allocator for Darwin.  This means jemalloc won't be hooked as
    the default allocator on OSX/iOS.

--enable-utrace
    Enable utrace(2)-based allocation tracing.  This feature is not broadly
    portable (FreeBSD has it, but Linux and OS X do not).

--enable-xmalloc
    Enable support for optional immediate termination due to out-of-memory
    errors, as is commonly implemented by "xmalloc" wrapper function for malloc.
    See the "opt.xmalloc" option documentation for usage details.

--enable-lazy-lock
    Enable code that wraps pthread_create() to detect when an application
    switches from single-threaded to multi-threaded mode, so that it can avoid
    mutex locking/unlocking operations while in single-threaded mode.  In
    practice, this feature usually has little impact on performance unless
    thread-specific caching is disabled.

--disable-tls
    Disable thread-local storage (TLS), which allows for fast access to
    thread-local variables via the __thread keyword.  If TLS is available,
    jemalloc uses it for several purposes.

--disable-cache-oblivious
    Disable cache-oblivious large allocation alignment for large allocation
    requests with no alignment constraints.  If this feature is disabled, all
    large allocations are page-aligned as an implementation artifact, which can
    severely harm CPU cache utilization.  However, the cache-oblivious layout
    comes at the cost of one extra page per large allocation, which in the
    most extreme case increases physical memory usage for the 16 KiB size class
    to 20 KiB.

--with-xslroot=<path>
    Specify where to find DocBook XSL stylesheets when building the
    documentation.

--with-lg-page=<lg-page>
    Specify the base 2 log of the system page size.  This option is only useful
    when cross compiling, since the configure script automatically determines
    the host's page size by default.

--with-lg-page-sizes=<lg-page-sizes>
    Specify the comma-separated base 2 logs of the page sizes to support.  This
    option may be useful when cross-compiling in combination with
    --with-lg-page, but its primary use case is for integration with FreeBSD's
    libc, wherein jemalloc is embedded.

--with-lg-size-class-group=<lg-size-class-group>
    Specify the base 2 log of how many size classes to use for each doubling in
    size.  By default jemalloc uses <lg-size-class-group>=2, which results in
    e.g. the following size classes:

      [...], 64,
      80, 96, 112, 128,
      160, [...]

    <lg-size-class-group>=3 results in e.g. the following size classes:

      [...], 64,
      72, 80, 88, 96, 104, 112, 120, 128,
      144, [...]

    The minimal <lg-size-class-group>=0 causes jemalloc to only provide size
    classes that are powers of 2:

      [...],
      64,
      128,
      256,
      [...]

    An implementation detail currently limits the total number of small size
    classes to 255, and a compilation error will result if the
    <lg-size-class-group> you specify cannot be supported.  The limit is
    roughly <lg-size-class-group>=4, depending on page size.

--with-lg-quantum=<lg-quantum>
    Specify the base 2 log of the minimum allocation alignment.  jemalloc needs
    to know the minimum alignment that meets the following C standard
    requirement (quoted from the April 12, 2011 draft of the C11 standard):

      The pointer returned if the allocation succeeds is suitably aligned so
      that it may be assigned to a pointer to any type of object with a
      fundamental alignment requirement and then used to access such an object
      or an array of such objects in the space allocated [...]

    This setting is architecture-specific, and although jemalloc includes known
    safe values for the most commonly used modern architectures, there is a
    wrinkle related to GNU libc (glibc) that may impact your choice of
    <lg-quantum>.  On most modern architectures, this mandates 16-byte alignment
    (<lg-quantum>=4), but the glibc developers chose not to meet this
    requirement for performance reasons.  An old discussion can be found at
    https://sourceware.org/bugzilla/show_bug.cgi?id=206 .  Unlike glibc,
    jemalloc does follow the C standard by default (caveat: jemalloc
    technically cheats if --with-lg-tiny-min is smaller than
    --with-lg-quantum), but the fact that Linux systems already work around
    this allocator noncompliance means that it is generally safe in practice to
    let jemalloc's minimum alignment follow glibc's lead.  If you specify
    --with-lg-quantum=3 during configuration, jemalloc will provide additional
    size classes that are not 16-byte-aligned (24, 40, and 56, assuming
    --with-lg-size-class-group=2).

--with-lg-tiny-min=<lg-tiny-min>
    Specify the base 2 log of the minimum tiny size class to support.  Tiny
    size classes are powers of 2 less than the quantum, and are only
    incorporated if <lg-tiny-min> is less than <lg-quantum> (see
    --with-lg-quantum).  Tiny size classes technically violate the C standard
    requirement for minimum alignment, and crashes could conceivably result if
    the compiler were to generate instructions that made alignment assumptions,
    both because illegal instruction traps could result, and because accesses
    could straddle page boundaries and cause segmentation faults due to
    accessing unmapped addresses.

    The default of <lg-tiny-min>=3 works well in practice even on architectures
    that technically require 16-byte alignment, probably for the same reason
    --with-lg-quantum=3 works.  Smaller tiny size classes can, and will, cause
    crashes (see https://bugzilla.mozilla.org/show_bug.cgi?id=691003 for an
    example).

    This option is rarely useful, and is mainly provided as documentation of a
    subtle implementation detail.  If you do use this option, specify a
    value in [3, ..., <lg-quantum>].

The following environment variables (not a definitive list) impact configure's
behavior:

CFLAGS="?"
    Pass these flags to the compiler.  You probably shouldn't define this unless
    you know what you are doing.  (Use EXTRA_CFLAGS instead.)

EXTRA_CFLAGS="?"
    Append these flags to CFLAGS.  This makes it possible to add flags such as
    -Werror, while allowing the configure script to determine what other flags
    are appropriate for the specified configuration.

    The configure script specifically checks whether an optimization flag (-O*)
    is specified in EXTRA_CFLAGS, and refrains from specifying an optimization
    level if it finds that one has already been specified.

CPPFLAGS="?"
    Pass these flags to the C preprocessor.  Note that CFLAGS is not passed to
    'cpp' when 'configure' is looking for include files, so you must use
    CPPFLAGS instead if you need to help 'configure' find header files.

LD_LIBRARY_PATH="?"
    'ld' uses this colon-separated list to find libraries.

LDFLAGS="?"
    Pass these flags when linking.

PATH="?"
    'configure' uses this to find programs.

=== Advanced compilation =======================================================

To build only parts of jemalloc, use the following targets:

    build_lib_shared
    build_lib_static
    build_lib
    build_doc_html
    build_doc_man
    build_doc

To install only parts of jemalloc, use the following targets:

    install_bin
    install_include
    install_lib_shared
    install_lib_static
    install_lib
    install_doc_html
    install_doc_man
    install_doc

To clean up build results to varying degrees, use the following make targets:

    clean
    distclean
    relclean

=== Advanced installation ======================================================

Optionally, define make variables when invoking make, including (not
exclusively):

INCLUDEDIR="?"
    Use this as the installation prefix for header files.

LIBDIR="?"
    Use this as the installation prefix for libraries.

MANDIR="?"
    Use this as the installation prefix for man pages.

DESTDIR="?"
    Prepend DESTDIR to INCLUDEDIR, LIBDIR, DATADIR, and MANDIR.  This is useful
    when installing to a different path than was specified via --prefix.

CC="?"
    Use this to invoke the C compiler.

CFLAGS="?"
    Pass these flags to the compiler.

CPPFLAGS="?"
    Pass these flags to the C preprocessor.

LDFLAGS="?"
    Pass these flags when linking.

PATH="?"
    Use this to search for programs used during configuration and building.

=== Development ================================================================

If you intend to make non-trivial changes to jemalloc, use the 'autogen.sh'
script rather than 'configure'.  This re-generates 'configure', enables
configuration dependency rules, and enables re-generation of automatically
generated source files.

The build system supports using an object directory separate from the source
tree.  For example, you can create an 'obj' directory, and from within that
directory, issue configuration and build commands:

    autoconf
    mkdir obj
    cd obj
    ../configure --enable-autogen
    make

=== Documentation ==============================================================

The manual page is generated in both html and roff formats.  Any web browser
can be used to view the html manual.  The roff manual page can be formatted
prior to installation via the following command:

    nroff -man -t doc/jemalloc.3